Our research is directed toward delineating the machinery employed by mammalian cells in culture to control and translate genetic information. The current genetic methodology applicable to somatic cells is very limited and often difficult to interpret. For this reason, we are devoting a major proportion of our research effort towards expanding the genetic tools available to researchers in mammalian cell biology and mammalian virology. In particular, we are developing the technology for isolating suppressor sensitive (i.e., nonsense) mutants in mammalian cells and their viruses. Such mutants are particularly useful because: a) they exhibit a clear mutant phenotype (i.e., they are not subject to a comparable "leakage" problem observed with temperature sensitive mutants of mammalian cells and their viruses), and b) they can be employed for physically identifying the gene product. The availability of such mutants would prove an invaluable tool for studying the numerous cellular aberrations of viral origin.